Overgrowth can turn grasses from landscape jewels to eyesores, so cut them back yearly in the spring before new shoots grow tall. Spring is the best trimming season, with snow and wildfires making fall a strong alternative.
This article covers all the details on when to cut back ornamental grasses, with practical tips, expert opinions, and a simple schedule to follow.
Quick Reference: Ornamental Grass Cutting Schedule
| Type of Ornamental Grass | When to Cut | Cutting Height |
| Warm-Season Grasses *Cut back in late fall if in a wildfire-prone zone | Late fall to mid-spring (November to April) | Cut 3 to 6 inches above the ground level. |
| Cool-Season Grasses | Late winter to early spring (February to March) | Cut 2/3 of the height and leave 1/3. |
| Evergreen Grasses *Only if necessary | Late winter to early spring (February to March) | Cut no more than 1/3 to 1/2 of the plant’s height. |
What happens if you don’t cut back ornamental grasses? The dead material smothers new growth, gives the bundle an unsightly look, and exposes the plant to mold, mildew, and pests.
Pro Tip: If your grasses are heavy seeders, prune the flower stalks before seeding to prevent them from spreading. Or hire a landscaping professional to cut your ornamental grasses at just the right time.
Types of Ornamental Grasses
Perennial ornamental grasses are deciduous or evergreen. Evergreen grasses stay green year-round and must be cut back only if severely damaged.
The foliage of deciduous grasses dries out in summer or winter when they go dormant, so it needs to be cut back yearly to make room for the new shoots. Deciduous grasses are either warm- or cool-season grasses:
- Warm-season ornamental grasses thrive at 80 F to 95 F and grow best in the country’s southern half. They start growing in late spring and go dormant in late fall.
- Cool-season ornamental grasses grow best at temperatures between 60 F and 75 F and are better adapted to northern climates. They grow the most in spring and fall and go dormant during summer.
When choosing the best types of ornamental grasses for your yard, consider grasses native to your area. They are better adapted to your climate, hardier, and easier to care for.
When to Cut Back Warm-Season Ornamental Grasses
Photo Credit: Bob Harvey / Wikimedia Commons / CC BY-SA 2.0
Warm-season grasses can be cut back from late fall, when they enter dormancy, to mid-spring, before they grow again.
Popular warm-season ornamental grasses:
- Pampas grass (a tall ornamental grass, great for privacy fences)
- Purple fountain grass
- Switchgrass
- Maiden grass
- Zebra grass
Why Spring is the Best Time to Cut
Warm-season grasses’ frosted seedheads look stunning in winter landscapes and provide food for overwintering insects and birds (a valuable addition in yards certified as wildlife habitats). The dry material also protects the crown from dry winds and freezing temperatures.
Christopher Enroth, horticulture educator for the University of Illinois Extension, says a good time to trim is “once we start to see green growth begin to emerge at the base of the plant.” This usually means to cut back warm-season grasses from March to April, but timing varies with location.
| Signs it is time to cut: Old dry foliage with green shoots emerging at the base. |
When Fall Cutting Makes Sense
Cutting your warm-season ornamental grasses in the fall, as soon as they dry out, is a must if you live in a state with a high risk of wildfires. Dry grass material can easily spread the fire on your property.
It’s also a good idea to trim your ornamental grasses in the fall if:
- Heavy snow flattens the grasses during winter.
- Plants have a foliar disease.
- You enjoy a tidy winter landscape.
Cut back your warm-season grasses after they enter dormancy, usually in October or November.
| Signs it is time to cut: Grass stems and blades turn fully brown and dry, and outer stems collapse outward. |
See Related: 6 Main Benefits of Fall Yard Cleanup
When to Cut Back Cool-Season Ornamental Grasses
Photo Credit: David J. Stang / Wikimedia Commons / CC BY-SA 4.0
The best time to cut cool-season ornamental grasses is late winter to early spring, from February to March.
Popular cool-season ornamental grasses:
- Blue sheep’s fescue
- Eastern bottlebrush
- Northern sea oats
- Mexican feather grass.
Why Cut Back in Late Winter to Early Spring
In late winter to early spring, cool-season grasses develop new shoots among the old foliage. Cutting back the dry leaves exposes the crown and shoots to more sunlight and speeds up growth.
Wait until the plant shows signs of exiting dormancy. Cutting too early risks exposing young, vulnerable shoots to late frosts.
| Signs it is time to cut: Fresh green growth at the center of the clump. |
When to Cut Back Evergreen Ornamental Grasses
Photo Credit: David J. Stang / Wikimedia Commons / CC BY-SA 4.0
The best time to lightly prune or cut back evergreen ornamental grasses is late winter to early spring (February to March).
Popular evergreen ornamental grasses:
- Mondo grass
- Blue oat grass
- Mountain sedge
- San Diego sedge
- Tufted hair grass.
Why Cut in Late Winter to Early Spring
Cutting back (or lightly trimming) early in the season allows evergreen grasses to recover in the mild spring weather, with plenty of time to strengthen for summer stress.
Evergreen ornamental grasses don’t need to be cut back yearly. Instead, they benefit from light grooming to remove old flower stalks and comb out dry foliage. Only cut back bundles with extensive damage, and don’t remove more than 1/2 of the height.
| Signs it is time to cut back: Clumps with extensive browning. |
Pro Tip: Many grasses, sedges, and rushes are evergreen in mild climates but deciduous in cold areas (e.g., pampas grass).
How Can You Tell If Your Ornamental Grass Is Warm-Season, Cool-Season, or Evergreen?
You can tell if your ornamental grass is warm-season, cool-season, or evergreen by its growing pattern:
- Evergreen: It stays green year-round.
- Warm-season: It turns brown late in the fall.
- Cool-season grass: It grows new shoots late winter to early spring.
You can also take a picture of the plant and check it online with Google Lens, or use a plant identification app like iNaturalist or PlantNet.
When Should You Divide Ornamental Grasses?
The best time to divide your ornamental grasses is when they are actively growing but before flowering. By type of ornamental grass, this means:
- Warm-season grasses: Spring through mid-summer.
- Cool-season grasses: Late winter to early spring and late summer to mid-fall.
- Evergreen grasses: Spring.
How do you know your grass needs division and not just cutting back? Mature grasses, 3 to 5 years old, die back in the center, get thinner, and the color is less vibrant.
FAQ
If you live up North, you might need to cut your ornamental grasses 2 to 3 weeks later in the spring since the weather warms up more slowly. Homeowners in the South may need to cut back the ornamental grasses earlier since soil and air temperatures rise faster.
It’s too late to cut the ornamental grass if new shoots have grown tall enough that you’ll clip them when cutting back the grass at the right height.
Cutting at this time is still okay, but expect your grass to look untidy for a while. “You may have an odd-looking clump of ornamental grass at first, but the grass will regrow and look fine by the end of summer when most begin to produce flowers and seedheads,” says Enroth, referring to warm-season grasses. Cool-season beauties typically get back their neat look by late spring.
Morning is a better time of day to cut back ornamental grasses. The air is cooler, plants are less stressed, and if you clip new growth, the wounds have plenty of time to heal before evening.
Make a Pro Decision on Trimming Ornamental Grasses
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Sources:
- Chris Enroth, horticulture educator at University of Illinois Extension, Macomb, IL. Personal interview.
- “Facts + Statistics: Wildfires.” By Insurance Information Institute.
- “Is it Too Late to Cut Back Ornamental Grasses?” By Christopher Enroth, horticulture expert. University of Illinois Extension.
- “Ornamental Grasses.” By David H. Trinklein, adjunct associate professor and state extension specialist in Floriculture. University of Missouri Extension.
Main Image Credit: Shutterstock
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